The present invention relates to a configuration for fuse initialization having at least one fuse bank which has a number of fuses in which redundant information is stored. The fuse bank can be read by a first and a second initialization signal, which are produced by a generator device. In each case one latch is associated with each fuse. The term xe2x80x9cfusesxe2x80x9d is in this case also intended to mean antifuses. The invention is preferably used in a memory whose memory cell array is subdivided into quadrants along which the fuse banks extend.
Redundant information that is stored in fuses is read to latches (locking elements) upon activation or start-up of a memory, for example a DRAM (Dynamic Random Access Memory). These latches buffer-store the redundant information and are located immediately adjacent to the fuses. In this case, each fuse has an associated latch.
Two initialization signals are required to read in redundant information, namely a first initialization signal bFPUP (bar fuse power up), which is an enabled signal, and a second initialization signal, FPUN, which is a control signal for latching in the redundant information and consists of a pulse which allows the redundant information to be buffer-stored in the latches for its duration.
FIG. 4 schematically shows a memory having a memory cell array including four quadrants Q1 to Q4, and fuse banks 5 to 12 that are located between these quadrants Q1 to Q4. The fuse banks 5 and 6 are associated with the quadrant Q1, while the fuse banks 7 and 8 are associated with the quadrant Q2, the fuse banks 9 and 10 are associated with the quadrant Q3, and the fuse banks 11 and 12 are associated with the quadrant Q4. In this case, the fuse banks 5 and 6 are located along two sides of the quadrant Q1, which are opposite the adjacent quadrants Q4 and Q2 and spaced away by a gap. A corresponding situation applies to the fuse banks 7 and 8 with respect to the quadrant Q2, to the fuse banks 9 and 10 with respect to the quadrant Q3, and to the fuse banks 11 and 12 with respect to the quadrant Q4. The fuses in the fuse banks 5 to 12 are in this case each associated with individual segments or arrays of the quadrants Q1 to Q4.
FIG. 5 shows a fuse F with an associated latch L. The fuse F is connected in series with a series circuit, which includes an n-channel MOS transistor T1 and a p-channel MOS transistor T2. The combination of the series circuit and the fuse F is connected between a fixed potential (frame or ground) and a supply voltage Vint. The first initialization signal bFPUP is applied to the gate of the transistor (T2), while the second initialization signal (FPUN) is applied to the gate of the transistor T1.
The node between the two transistors T1 and T2 is connected to the input of a first inverter I1 and to the output of a second inverter I2 that is downstream from the first inverter I1. In addition, the output of the first inverter I1 is connected to the control input of a first controlled switch S1, while the output of the second inverter I2 is connected to the control input of a second controlled switch S2.
A first signal A1 is applied to the input of the first switch S1, while a second signal A2 is applied to the input of the second switch S2.
FIG. 6 shows the profile of the supply voltage Vint, the profile of the first initialization signal bFPUP, and the profile of the second initialization signal FPUN as a function of time T.
When the supply voltage Vint is switched on, that is to say is high, the transistor T2 is switched on, while the transistor T1 is still switched off, since both signals bFPUP and FPUN are low. The supply voltage Vint is thus applied to the input of the latch L, so that its pre-initialization takes place. If the first initialization signal bFPUP then changes to high (flank F2), the transistor T2 then is switched off. The latch L is thus disconnected from the supply voltage Vint. Once the second initialization signal, or pulse, FPUN has been switched on (flank F3), the transistor T1 is switched on, while the transistor T2 is switched off and the fuse information from the fuse F is thus supplied to the latch L. Depending on the content of this information (xe2x80x9c1xe2x80x9d) or (xe2x80x9c0xe2x80x9d), the switch S1 is switched on, while the switch S2 is switched off, or the switch S1 is switched off while the switch S2 is switched on. This writing process for the fuse information is terminated with the end of the pulse FPUN (flank F4). The signal A1 or the signal A2 is thus produced at an output A of the switches S1 and S2, depending on the fuse information for the fuse F.
FIG. 7 shows one possible signal profile, which occurs when the first initialization signal bFPUP starts up together with the supply Vint. In this case, the pre-initialization of the latch L takes place on the trailing edge (flank F1) of the signal (bFPUP).
The two initialization signals bFPUP and FPUN must be supplied to all of the fuses in the fuse banks 5 to 12 upon activation of the memory, so that these fuses can read their respective information to the associated latches. Each individual fuse F has an associated latch L of the type shown in FIG. 5. Other circuit configurations may, of course, also be chosen for the latches L in this case.
In order to allow the initialization with the two initialization signals bFPUP and FPUN, lines 13 are routed in the form of loops along the fuse banks 5 to 12. FIG. 4. shows one of the lines 13, in the form of dashed lines, for the first initialization signal bFPUP. A corresponding line loop is required for the second initialization signal FPUN.
The first initialization signal bFPUP thus first of all runs on the line 13 along the fuse bank 5 from the center of the memory to its edge, and then along this fuse bank 5 back again, in order then to be routed successively in a corresponding manner through the fuse banks 6 to 12.
Since the same situation also applies to the second initialization signal FPUN and to its line, this means that a total of four lines are in each case required along the fuse banks 5 to 12 and along mutually adjacent sides of the quadrants Q1 to Q4.
Thus, in a corresponding way to the scheme shown in FIG. 4, the fuse initialization process runs sequentially over the entire chip of the memory, which results in a uniform current distributed over time, which is advantageous for starting up, during the initialization phase.
Depending on the chip architecture of a memory, the area consumed by individual areas on the chip may be dominated by transistors or by lines. In the latter case, a saving of lines reduces the area, which is a considerable advantage. This is particularly true when additional transistors are required due to the saving of lines.
It is accordingly an object of the invention to provide a configuration for fuse initialization which overcomes the above-mentioned disadvantageous of the prior art apparatus of this general type. In particular, it is an object of the invention to provide a configuration for fuse initialization, in which it is possible to reduce the area that is required on a chip.
With the foregoing and other objects in view there is provided, in accordance with the invention, a configuration for fuse initialization, that includes: a plurality of latches; a plurality of fuse banks, each one of the plurality of the fuse banks having a plurality of fuses storing redundant information, each one of the plurality of the fuses associated with a respective one of the plurality of the latches; a generator device for generating a plurality of initialization signals which are used for reading the plurality of the fuses, the plurality of initialization signals including a first initialization signal and a second initialization signal; a plurality of first lines and a plurality of second lines; and a memory cell array having four quadrants, each one of the quadrants having edges that are adjacent to others of the quadrants. Each one of the plurality of the fuse banks is located along a respective one of the edges of one of the quadrants. Each one of the plurality of the fuse banks serially receives the first initialization signal from a respective one of the first lines and the second initialization signal from a respective one of the second lines. The respective one of the first lines and the respective one of the second lines are different lines. The respective one of the first lines and the respective one of the second lines each have a beginning and an end at which ones of the plurality of the initialization signals are delayed.
In the configuration for fuse initialization of the type mentioned initially, the object of the invention is achieved because the first initialization signal is carried along a first line to the fuses, and the second initialization signal is fed back on a second line with a delay.
Of the four lines mentioned in the background, which are each associated with one fuse bank, is thus possible to save a total of two lines which, with respect to these lines, means a surface area reduction of about 50%. To this end, circuits which detect a change in the first initialization signal and then, in each case, pass back the other initialization signal on the other line with a delay are integrated at the end of the quadrant of the memory cell array, or of corresponding chip areas. In addition to the generator device for the two initialization signals, a circuit which detects the signals sent back and feeds them with a time delay into the area of the next fuse bank is integrated in the center region of the memory, or in the chip center.
In accordance with an added feature of the invention, it is also possible to control the generator device for the initialization signals such that it feeds the two initialization signals into the areas of the individual fuse bank, with a time delay.
The invention makes it possible to save two lines, on the inside of a quadrant of the memory cell array, that is to say a total of 2xc3x972xc3x974=16 lines over the entire chip for the memory, by providing appropriate receiving and transmitting circuits, which detect the initialization signals and pass them on with a time delay, at each of the ends of the areas of the individual fuse banks.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a configuration for fuse initialization, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.